1. Technical Field of the Invention
The present invention relates to integrated circuit output amplifiers and, more particularly, but not by way of limitation, embodiments of the present invention relate to a complimentary metal oxide semiconductor (CMOS) technology output amplifier with an output stage impedance that is variable as a function of the environmental parameters of the amplifier's constituent CMOS transistors.
2. Description of Related Art
An output amplifier is used to transmit electrical signals outwards from a circuit. Generally, signals are supplied to electrical conductors (pins, tracks) that can assimilate inductive and capacitive loads. The function of the output amplifier is mainly to adapt the signal emitted outwards from the circuit to a power line receiving the signal.
An amplifier output stage conventionally includes a pair of complementary (buffer) MOS transistors forming an output stage.
The output stage impedance varies considerably as a function of the environment parameters of the transistors such as the temperature, the supply voltage and the silicon manufacturing conditions (in-silicon manufacturing process). Two important consequences derive from this.
The first lies in the fact that the integrity of the output signal may be degraded, given the difference in impedance between the power line receiving the signal and the output stage.
The second lies in the fact that, when the transistors are fast, the maximum current peak is much larger, which generates excessive noise on the power supply terminals.
Embodiments of the present invention provide a solution to the aforementioned problems.